A method was developed to measure the rate of incorporation of palmitate, Jpalm, from plasma into different brain regions in the awake rat. Jpalm did not change between 3 and 34 months of age, indicating that the rate of turnover of palmitate-containing brain lipids was unchanged. During development of the rat, the time course of Jpalm corresponded to the time course of myelination in the developing brain. Jpalm fell in central auditory pathways following damage to the cochlea. Following a 5 minute period of bilateral ischemia, gerbils had reduced palmitate incorporation into the irreversibly damaged CA 1 region of the hippocampus but increased incorporation into reversibly affected regions. Palmitate incorporation into the hypoglossal nucleus increased maximally 24 days after hypoglossal nerve axotomy. This increase correlated with regenerative processes. Following axotomies in which nerve endings were sealed, palmitate incorporation was decreased at 24-35 days.